1. Field of the Invention
The present invention relates to a control device of a droplet ejection head, a control method and a program storage medium, and particularly relates to a control device, control method and program storage medium of a droplet ejection head at which a nozzle face is wiped for cleaning.
2. Description of the Related Art
A droplet ejection device (for example, an inkjet printer) that ejects liquid droplets such as ink from nozzles of a droplet ejection head (hereinafter referred to as a head) and forms an image, a pattern or the like at a recording medium has been known heretofore. In such a droplet ejection device, a maintenance unit is provided in order to excellently preserve ink ejection conditions of the head. The maintenance unit is provided with a wiper blade, which is a rubber plate or the like that wipes and removes foreign matter and the like adhering to a nozzle face, and a suction pump, which is connected via a cap for sucking and removing air bubbles in the nozzles, or the like.
When a nozzle face, in which ejection apertures of nozzles 80a of a head 80 are arrayed, is to be wiped for cleaning by a cleaning member such as a wiper blade, usually, ink is caused to exude to the exterior of the nozzle face, as shown in FIG. 7A. Adherents such as hardened ink, dirt, paper dust are immersed in the ink and dissolved or loosened from the nozzle face, and are then wiped off by the cleaning member. The exuded ink also acts as a lubricant between the nozzle face and the cleaning member and prevents damage to the surface of the head 80 during wiping by the wiper blade.
As a device with such a maintenance function, an inkjet application device is known (see Japanese Patent Application Laid-Open (JP-A) No. 2006-88067) that: applies a certain pressure within an ink tank, which is connected to an ink application head via ink supply piping; causes ink to exude to the exterior of a nozzle face provided at a distal end of the ink application head; causes the ink to project from the nozzle face within a range such that the ink does not drip in accordance with surface tension of the ink; and removes an ink surface that is formed at the exterior of the nozzle face.
However, even within the range in which ink does not drip because of surface tension, as shown in FIG. 7B, when the ink exuded from one nozzle 80a comes into contact with the ink exuded by neighboring nozzles 80a, the ink aggregates together and the exuded ink moves. As described above, adherents such as hardened ink, dirt, paper dust and the like are dissolved or loosened from the nozzle face by being immersed in the ink. However, if the exuded ink moves from nozzle peripheries, adherents near to the nozzles 80a, which will affect ejection, may not be immersed in the ink. As a result, the adherents may not be thoroughly removed. Moreover, when the ink aggregates together, the ink may drip due to its own weight. If this happens, in addition to thorough cleaning not being possible, a device interior may be soiled.
Furthermore, the surface tension of an ink varies with factors such as aging deterioration, ambient temperature. Therefore, even if ink is exuded under conditions such that the ink does not drip as in the above-mentioned technology described in JP-A No. 2006-88067, if the surface tension has changed because of aging deterioration of the ink, an ambient temperature or the like, the ink may drip and soil a device interior, and if an amount of exuded ink is insufficient, the surface of the head 80 may be damaged.